Method and apparatus for water management in direct methanol fuel cell system using heat exchanger

Abstract

A method and an apparatus for water management in a direct methanol fuel cell system using a heat exchanger and including a pipe for connecting a cathode outlet of a fuel cell stack with a mixer. The method includes: measuring an output voltage and/or an output current of the fuel cell stack; extracting a concentration value of the mixed fuel corresponding to the measured output voltage and/or current from a look-up table; comparing the extracted concentration value of the mixed fuel with a reference concentration value; and forcibly cooling a fluid flowing in a pipe for a time period by a heat exchanger coupled to the pipe when the extracted concentration value of the mixed fuel is higher than the reference concentration value.

1 . A method for water management in a direct methanol fuel cell system comprising a mixer for supplying an anode electrode of a fuel cell stack with a mixed fuel, the mixed fuel comprising an unreacted fuel and water coming out from the fuel cell stack and a high concentration fuel supplied from a fuel feeder, the method comprising: 
 measuring an output voltage and/or an output current of the fuel cell stack;    extracting a concentration value of the mixed fuel corresponding to the measured output voltage and/or current from a look-up table;    comparing the extracted concentration value of the mixed fuel with a reference concentration value; and    forcibly cooling a fluid flowing in a pipe for a time period by a heat exchanger coupled to the pipe when the extracted concentration value of the mixed fuel is higher than the reference concentration value,    wherein the pipe is for connecting a cathode outlet of the fuel cell stack with the mixer.    
   
   
       2 . The method according to  claim 1 , wherein the forcibly cooling the fluid flowing in the pipe comprises turning on the heat exchanger to supply external air to an exposed part of the pipe.  
   
   
       3 . The method according to  claim 1 , further comprising: 
 stopping the heat exchanger from forcibly cooling when the extracted concentration value of the mixed fuel is not higher than the reference concentration value.    
   
   
       4 . The method according to  claim 3 , further comprising: 
 increasing an amount of a high concentration fuel supplied from the fuel feeder for a second time period when the extracted concentration value of the mixed fuel is lower than the reference concentration value.    
   
   
       5 . The method according to  claim 3 , wherein the forcibly cooling the fluid flowing in the pipe comprises turning on the heat exchanger to supply external air to an exposed part of the pipe.  
   
   
       6 . The method according to  claim 5 , wherein the stopping the heat exchanger from forcibly cooling comprises turning off the heat exchanger.  
   
   
       7 . The method according to  claim 5 , wherein the stopping the heat exchanger from forcibly cooling comprises blocking the heat exchanger from supplying external air to the exposed part of the pipe while leaving the heat exchanger turned on.  
   
   
       8 . A method for water management in a direct methanol fuel cell system comprising a circulator of storing an unreacted fuel and water coming out from a fuel cell stack, and a mixer for providing a mixed fuel by mixing a low concentration fuel from the circulator and a high concentration fuel from a fuel feeder and for supplying the mixed fuel to the fuel cell stack, the method comprising: 
 sensing a concentration of the low concentration fuel;    comparing a concentration value of the low concentration fuel corresponding to the sensed concentration with a reference concentration value; and    forcibly cooling fluid flowing in a pipe for a time period by a heat exchanger coupled to the pipe when the extracted concentration value of the low concentration fuel is higher than the reference concentration value,    wherein the pipe is for connecting a cathode outlet of the fuel cell stack with the circulator.    
   
   
       9 . The method according to  claim 8 , wherein the forcibly cooling the fluid flowing in the pipe comprises turning on the heat exchanger to supply external air to an exposed part of the pipe.  
   
   
       10 . The method according to  claim 8 , further comprising: 
 stopping the heat exchanger from forcibly cooling when the extracted concentration value of the mixed fuel is not higher than the reference concentration value.    
   
   
       11 . The method according to  claim 10 , further comprising: 
 increasing an amount of a high concentration fuel supplied from the fuel feeder for a second time period when the extracted concentration value of the mixed fuel is lower than the reference concentration value.    
   
   
       12 . The method according to  claim 8 , further comprising: 
 measuring an output voltage and/or an output current of the fuel cell stack;    extracting a concentration value of the mixed fuel corresponding to the measured output voltage and/or current from a look-up table;    comparing the extracted concentration value of the mixed fuel with a second reference concentration value; and    forcibly cooling a fluid flowing in a second pipe for a second time period by a second heat exchanger coupled to the second pipe when the extracted concentration value of the mixed fuel is higher than the second reference concentration value,    wherein the second pipe is for connecting a cathode outlet of the fuel cell stack with the mixer.    
   
   
       13 . The method according to  claim 8 , wherein the forcibly cooling the fluid flowing in the pipe comprises providing a heat exchanging fluid through the heat exchanger to exchange heat with an exposed part of the pipe.  
   
   
       14 . An apparatus for water management in a direct methanol fuel cell system comprising a mixer for supplying an anode electrode of a fuel cell stack with a mixed fuel, the mixed fuel comprising an unreacted fuel and water coming out from the fuel cell stack and a high concentration fuel supplied from a fuel feeder, the apparatus comprising: 
 a heat exchanger adjacent to a pipe connecting a cathode outlet of the fuel cell stack with the mixer, and for condensing fluid passing through the pipe; and    a controller for measuring an output voltage and/or current of the fuel cell stack, for extracting a concentration value of the mixed fuel corresponding to the measured output voltage and/or current from a previously stored look-up table, and for increasing an amount of fluid condensation by operating the heat exchanger when the extracted concentration value of the mixed fuel is higher than a previously stored reference concentration value.    
   
   
       15 . The apparatus according to  claim 14 , wherein the mixer comprises: 
 a circulator for receiving the unreacted fuel and water from an anode electrode and a cathode electrode of the fuel cell stack, respectively, and for storing the unreacted fuel and water as a low concentration fuel; and    a fuel mixer for receiving the low concentration fuel and the high concentration fuel and for supplying the mixed fuel of the low concentration fuel and the high concentration fuel to the anode electrode of the fuel cell stack.    
   
   
       16 . The apparatus according to  claim 15 , further comprising a concentration sensor internally provided in a fuel transferring pipe connecting the circulator and the fuel mixer, and for sensing a concentration of the low concentration fuel passing through the fuel transferring pipe.  
   
   
       17 . The apparatus according to  claim 16 , wherein the controller decreases a time period for supplying the low concentration fuel by a pump from the circulator to the fuel mixer when the extracted concentration value of the mixed fuel is not higher than the reference concentration value.  
   
   
       18 . The apparatus according to  claim 16 , wherein the concentration sensor comprises at least one of an ionic conduction polymer resin or a complex resin.  
   
   
       19 . The apparatus according to  claim 16 , wherein a volume of the concentration sensor is according to a concentration of methanol in the low concentration fuel.  
   
   
       20 . The apparatus according to  claim 14 , wherein the controller increases a supplying amount of the high concentration fuel supplied from the fuel feeder for a predetermined time when the extracted concentration value of the mixed fuel is lower than the reference concentration value.